The general concept is the following: I have the HTG3533 humidity sensor and want to interface it with an ADC that has an internal voltage reference of 1.2V
What I plan to do is to use a voltage divider, consisting of two 1MΩ resistors. Thus, the output voltage of the sensor will be divided by 2 and be always in the input range of the ADC. After the voltage divider, I'll put a buffer constructed around an LPV511 OpAmp in order to provide small output resistance for the connection to the ADC.
Moreover, I would like to put an RC low-pass filter (something like a 5k with a 1 or 10u) in order to filter out any noise at the output line of the sensor, since the sensor will be located at a distance from the interface PCB.
My question is : Where to put this filter? Before the resistive network, just at the entrance of the signal at the PCB or after the buffer and before the ADC? I think that the best is to put it before the voltage divider. Is this correct?
I also have a (quite silly) question with this design: the data-sheet of the sensor says that its output impedance is 50Ω. Is there any problem that this small resistance is going to be connected to a huge input resistance of the analogue front-end? (As I said, I have a voltage divider consisting of two 1MΩ resistors. Their value can of course be reduced)
Thanks
Nikos
What I plan to do is to use a voltage divider, consisting of two 1MΩ resistors. Thus, the output voltage of the sensor will be divided by 2 and be always in the input range of the ADC. After the voltage divider, I'll put a buffer constructed around an LPV511 OpAmp in order to provide small output resistance for the connection to the ADC.
Moreover, I would like to put an RC low-pass filter (something like a 5k with a 1 or 10u) in order to filter out any noise at the output line of the sensor, since the sensor will be located at a distance from the interface PCB.
My question is : Where to put this filter? Before the resistive network, just at the entrance of the signal at the PCB or after the buffer and before the ADC? I think that the best is to put it before the voltage divider. Is this correct?
I also have a (quite silly) question with this design: the data-sheet of the sensor says that its output impedance is 50Ω. Is there any problem that this small resistance is going to be connected to a huge input resistance of the analogue front-end? (As I said, I have a voltage divider consisting of two 1MΩ resistors. Their value can of course be reduced)
Thanks
Nikos